Oxidation of olefins to acids

ABSTRACT

1. IN A PROCESS FOR THE CATALYTIC OXIDATION OF AN ALIPHATIC OLEFIN TO CARBOXYLIC ACIDS WITH A PERACID OXIDIZING AGENT IN THE PRESENCE OF RUTHENIUM CATALYST THE IMPROVEMENT WHICH COMPRISES ADDING TO THE REACTION MIXTURE AN ALKALI METAL SALT OF A LOWER FATTY, ACID, OR CARBONATE.

United States Patent 01 fice Patented Oct. 1, 1974 3,839,375 OXIDATIONOF OLEFINS T ACIDS Ming Nan Sheng, Cherry Hill, N.J., assignor toAtlantic Richfield Company, Philadelphia, Pa. N0 Drawing. Filed Nov. 9,1972, Ser. No. 305,202 Int. Cl. C08h 17/36 US. Cl. 260-413 11 ClaimsABSTRACT OF THE DISCLOSURE A process for converting aliphatic olefins,such as, octene-l, heptadecene, etc., to carboxylic acids, wherein theolefin is oxidized with a peracid, such as, performic, peracetic,persuccinic, etc., in the presence of a ruthenium catalyst, such as,ruthenium dioxide, ruthenium trichloride, etc., and a small amount of anorganic or inorganic base, such as, amines, alkali metal and alkalineearth metal hydroxides, carbonates, etc.

BACKGROUND OF THE INVENTION The present invention relates to a processfor the catalytic oxidation of olefins to produce carboxylic acids. Morespecifically, the present invention relates to a process for thecatalytic oxidation of aliphatic olefins to produce carboxylic acids inthe presence of a ruthenium catalyst, a peracid oxidizing agent and asmall amount of a base.

Fatty acids have heretofore been used commercially for the manufactureof synthetic lubricants and soaps. Consequently, the market for suchfatty acids has generally exceeded the ability of industry to supplythese materials from their sources. There is therefore a substantialdemand for such fatty acids, particularly those having long carbonchains.

In the past, numerous processes have been developed (for the productionof fatty acids from various related materials. In one such process, thevarious alcohols, such as, primary alcohols, were treated with anoxidizing agent in the presence of a catalyst, such as, ruthenium toproduce the corresponding fatty acids. In these processes, theconversion to fatty acid is generally quite low. Similarly, fatty acidshave heretofore been produced by the catalytic or noncatalytic oxidationof various olefins, usually primary olefins and cyclic olefins. In onesuch process, as disclosed in US. Pat. 2,585,129, a primary olefin isoxidized with hydrogen peroxide in the presence of peracetic acid toproduce the corresponding saturated dihydroxy hydrocarbon. Thereafter,the dihydroxy compound is selectively oxidized with periodic acid tocause cleavage between the acid contiguous hydroxylated carbons andthereby form a fatty aldehyde which, in turn, is further oxidized withperacetic acid to form the corresponding fatty acid. Obviously, thismulti-step process is time-consuming and, in addition, the yield offatty acid is quite low. In a similar process, as set forth in WestGerman Ofienlegungsschrift 2046034, an aliphatic or cyclic olefin isreacted with an oxidizing agent in the presence of a ruthenium catalyst.However, it has been found by carrying out the preferred technique ofthe German publication that a number of byproducts are produced, such asdiols, diol monoacetates, and diol diacetates and therefore, theproduction of the fatty acid is low. Accordingly,

these prior art processes have not been as successful as desired, to theextent that substantial amounts of starting materials are wasted or areconverted to other compounds which either must be discarded or oxidizedin a multistep process to produce the desired fatty acids.

It is therefore an object of the present invention to provide animproved process for converting aliphatic olefins to fatty acids.Another object of the present invention is to provide an improvedprocess for producing fatty acids from aliphatic olefins wherein a highselectivity to fatty acid is obtained. Another and further object of thepresent invention is to provide an improved process for the conversionof aliphatic olefins to fatty acids in the presence of a rutheniumcatalyst, peracid oxidizing agent and a base. Another and further objectof the present invention is to provide an improved process for theconversion of aliphatic olefins to fatty acids in the presence of aruthenium catalyst, a peracid oxidizing agent, a base, and an inertorganic solvent.

These and other objects and advantages of the present invention will beapparent from the following detailed description.

SUMMARY OF THE INVENTION The process for the conversion of olefins tofatty acids comprising contacting an aliphatic olefin with a peracidoxidizing agent in the presence of a ruthenium catalyst and a base.

DETAILED DESCRIPTION OF THE INVENTION The oxidation process of thepresent invention causes a cleavage between the contiguous double bondcarbons of the aliphatic olefin to form two moles of acids in accordancewith the following equation:

0 O ROOOH, RuCla R1CH=OHR RrooH RICOH wherein R and R may be alike ordifferent straight or branch chain alkyl radicals, aryl radicals,alkaryl radicals, aralkyl radicals, or hydrogen. Preferred R and R alkylradicals contain from 2 to about 40 carbon atoms at preferably about 2to 20 carbon atoms, such as ethyl, butyl, octyl and decyl; preferred Rand R aryl radicals include phenyl and naphthyl; suitable R and Raralkyl radicals include phenylethyl and naphthyl-butyl wherein thealkyl portion of the aralkyl radical may contain from 1 to about 6carbon atoms; preferred R and R aralkyl radicals include tolyl andmethylnaphthyl and include alkyl substituents of 1 to about 6 or morecarbon atoms.

The process may be employed to oxidize a wide variety of aliphaticolefins to yield high volumes of the desired acids. Where the termaliphatic olefin is utilized herein, it is meant to include any compoundhaving one or more double bonds in a straight chain either in a straightchain compound or as a substituent of a branched chain or cycliccompound. Generically, the olefins which may be employed include2-olefins, (ethylenically-unsaturated olefins) vinylidines and dieneshaving about 2-40 C's. Specific examples of suitable materials includeethylene, propylene, hexene-l, isobutylene, 4-methylhexene1, decene-l,I-S-hexenediene, 6-propyl decene-l, dodecene-l, dodecene triene-l, 4, 8,2-butyl-1-octene, pentadecene-l, hexadecene-l, eicosene, octadiene,pentacosene-6, nonacosene-3, hexatricotene-l, pentacontene-IS,4-ethyloctene-2, styrene, B-methyl-styrene, tetraphenylethylene,vinylnaphthalene, vinylanthracene, 4 butyl-l vinylnaphthalene,2,7-diphenyldodecene-3, hexane-1, octene-l, decene-l, dodecene-l,tetradecene-l, 8-heptadecene, isomers of decene, dodecene, tetradecene,hexadecene and eicosene, vinylcyclohexane, butadiene-1,3, andalkyl-substituted butadienes.

Normally between about 10 to 80% by weight of olefins should be present.

Where the term peracid is utilized in accordance with the presentinvention, this term is meant to include materials as defined in TheCondensed Chemical Dictionary, 6th Edition, Reinhold and Company, 1956.In accordance with this definition, peracids are derivatives of hydrogenperoxide the molecules of which contain one or more directly linkedpairs of oxygen atoms, OO. These peracids do not include permanganic,perchloric, and periodic acids. Suitable peracids for use in accordancewith the present invention are peracetic, performic, perphthalic,persuccinic, persulfuric, perboric, trichloroperacetic, trifluoroacetic,perbenzoic, m-chlorobenzoic, p-nitrobenzoic, etc.

A large amount of the peracid should be present in the reaction mixture.By way of example, this amount should be between about 1 to 105% byweight of the olefin. A preferred amount of peracid is between about 50to 100% by weight.

The catalyst utilized in accordance with the present invention isruthenium metal or an organic or inorganic ruthenium compound. Anyorganic or inorganic ruthenium salt having an anion which does notunduly restrict the formation of the desired products by an extraneousside reaction can be utilized as a catalyst. Salts of fatty acids havingup about four carbon atoms are preferred organic salts. Examples of suchcompounds include ruthenium formate, acetate, propionate or butyrate.Inorganic salts in general and simple inorganic salts in particularconstitute a highly preferred class of ruthenium-containing catalysts,such as, sulfides and oxides of ruthenium. In addition to the above,organo-metallic compounds, such as, bis (cyclopentadienyl) ruthenium andruthenium carbonyls, such as, Ru(CO) Ru (CO) (Ru(CO) Ru(CO) X, wherein Xis chlorine, bromine or iodine, may also be employed as catalysts. Awide variety of ruthenium chelates are also applicable in the presentprocess. Preferred chelates have a donor atom selected from the groupconsisting of Group VV and Group VI-B elements of the Periodic Table.Chelating agents having a donor atom selected from the class consistingof nitrogen and oxygen are quite efiective. Triamines, tetra-amines andoximes comprise a preferred class of chelating agents having nitrogen asa donor atom. Dibasic carboxylic acids are also a preferred class ofchelating agents having an oxygen as a donor atom. Thus, chelates,derived from well-known chelating agents, such as, salicylic acid,2-acyloin oxime, 2-benzoin oxime, dimethylglyoxime, acetylacetone,aminoacetic acid, oxalic acid, diethylenetriamine,triethylenetetraamine, malonic acid, and the like can be employed,Illustrative examples of such chelates include tris (ethylenediamine)ruthenium III, and the like.

As a general rule, the amount of ruthenium catalyst present in thereaction mixture should be between about 0.0001 and 1.0% by weight ofthe olefin. Preferably, the ruthenium catalyst is present in amountsbetween about 0.0001 and 0.001% by weight.

Suitable bases in accordance with the present invention may include anyorganic or inorganic base which does not interfere with the mainreaction. Organic bases, such as, primary, secondary, and tertiaryorganic amines such as triethylamine and pyridine are suitable. Metalsalts of fatty acids selected from metals of Group I-A and Group II-A ofthe Periodic System are preferred wherein the fatty acid has up to about4 carbon atoms. Inorganic bases, such as, Group I-A and Group H-A metalhydroxides, carbonates, phosphates and the like are particularlypreferred. The mole ratio of peracid to base should be between about 4to 1 and 100 to 1. Preferably, the peracid to base ratio should bebetween about 10 to 1 and 50 to l and, in most cases, should rangebetween about 25 to land 40 to 1.

The process is generally carried out in the presence of an organicsolvent. Specifically, any inert solvent which is not susceptible tooxidation can be utilized. Paraffinic hydrocarbons having about 5 to 30CS, halogenated hydrocarbons with about 4 Us, esters with about 2 to 20CS, etc., such as, pentane, hexane, heptane, etc. are preferred.Dichloromethane, ethyl acetate, and trifluoroacetic acid are alsouseful.

Suitable amounts of solvent are from about 25 to by weight of thereaction mixture and preferably, between about 25 and 75% by weight.

In the event that the peracid or the catalyst is not readily misciblewith the solvent, agitation may be advantageously employed.

The process of the invention described herein is generally carried outat the reflux temperature of the solvent and under atmospheric pressure.However, when olefins having a lower boiling point than the solvent areemployed, it is preferable to carry out the reaction under pressure. Anypressure above atmospheric may be utilized. However, pressures withinthe range of about 50 to 500 p.s.i.g. are preferred.

The following detailed examples illustrate the operation of the presentinvention.

EXAMPLE 1 Octene-l (11 g.) RuCl -3H 0 (0.05 g.), and hexane ml.) wereplaced in a one liter, 3-neck flask equipped with an addition funnel, athermometer, a mechanical stirrer and a reflux condenser. The reactionmixture was stirred to obtain a homogeneous dispersion of the rutheniumcompound in the organic solvent. At this time, a solution of 2.5 g.sodium acetate in 100 g. of 40% by weight peracetic acid was added. Anexothermic reaction took place. The peracid was added in a way such thatthe mixture was kept refluxing at about 64 C. After the addition wascompleted, the reaction mixture was allowed to reflux for an additionalhour and then cooled to room temperature. The reaction mixture formedtwo phases which were then separated. The aqueous phase acidified to apH of 1 with hydrochloric acid, was then extracted with two volumes of100 ml. of hexane. The combined hexane fractions were washed with 100ml. of water to secure complete elimination of the acetic acid. Thehexane layer was concentrated to a residue under reduced pressure. Theresidue was analyzed for fatty acids and found to contain 1.0 g.hexanoic acid, 10.3 g. heptanoic acid and 0.5 g. octanoic acid. Themolar selectivity to total acids was 93.0%.

EXAMPLE 2 The procedure of Example 1 was repeated except that theruthenium trichloride was replaced by ruthenium dioxide. In thisparticular example, the molar selectivity to total acids was 90% EXAMPLE3 The experimental procedure of Example 2 was repeated except thatsodium acetate was not added to the peracid. The molar selectivity inthis case was found to be 76.4%.

EXAMPLE 4 The experimental procedure of Example 2 was repeated exceptthat sodium acetate was replaced by sodium carbonate. The molarselectivity in this case was found to be 95.5

These, as well as additional examples made under varying conditions, aresummarized in Table I.

TABLE I Ruthenium catalyzed oxidation of octene-1 with peracetic acidExample number 5 6 7 8 9 10 11 12 3 2 1 4 Octene-1, g 35 35 35 35 35 3535 ll. 2 11 11 11 11 8-heptadecene, g- RuCh-1-3 H O, g- 0. O5 0. O5 0.05 0. 05 0. 05 0. 05 0 05 0. 05

RuO

Caacid,z 1.6 .8 0.6 0.9 1.0 1.0 C acid, g 0. 2 16. 8 11. 9 16. 6 17. 820. 7 22. 4 0 8. 8 10. 2 10. 3 10. 8 Cgacidm 4.2 0.6 0.8 .7 0.3 0.3 0.50.3 Ca acid, g- 4. 5

By-products, g. 5. 3 20.9 12. 9 12. 0 4. 7 4. 3 2 2. 6 1. 3 0. 6 Totalacids, g. 8. 9 16. 8 11.9 16. 6 17.8 22. 9 23. 2 5 9. 7 11. 4 11. 8 12.1 Total product 14. 2 36. 4 37. 6 37. 0 34. 1 33. 3 4 2. 3 12. 7 11. 812. 7 Conversion 100 90. 0 89. 7 76. 9 79. 4 81. 4 83. 4 .2 100 100 100100 Molar selectivity to total acids, percent 56. 5 33. 0 32. 5 53. 355. 2 69. 6 68. 3 70. 2 60 76. 4 90. 0 93. 0 95. 5

I German Patent publication. b Sodium carbonate was used in the place ofsodium acetate. 8 Peracetic acid.

l 4 Sodium acetate.

From the above example, it is clear that the runs made utilizing a baseare superior to those made under the conditions of German patentpublication 2,046,034 where no base was employed.

Runs were also made to determine the efiect of an added base on theconversion of cyclic olefins, having double bonds in a ring structure,to acids.

EXAMPLE 14 Following the procedure of Example 1, 8.2 .g. of cyclohexene,0.05 g. of RuCl 100 ml. of hexane, 100 g. of 40% peracetic acid and 2.5g. of sodium acetate were utilized. A yield of 74.3% by weight wasobtained.

EXAMPLE 15 Example 14 was repeated except that no sodium acetate Wasutilized. In this case, the yield was 71.2%.

It is obvious from Examples 14 and 15 that the addition of a base had nosignificant elfect on the reaction when the double bond is present in aring structure.

While specific materials and specific techniques have been disclosedherein, it is to be understood that these recitations as well as thespecific working examples are illustrative only and that numerousvariations and modifications of the process will be apparent to oneskilled in the art. Accordingly, the present invention is to be limitedonly in accordance with the appended claims.

I claim:

1. In a process for the catalytic oxidation of an aliphatic olefin tocarboxylic acids with a peracid oxidizing agent in the presence ofruthenium catalyst the improvement which comprises adding to thereaction mixture an alkali metal salt of a lower fatty, acid, orcarbonate.

2. A method in accordance with Claim 1 wherein the aliphatic olefin hasat least one double bond in a straight chain.

3. A method in accordance with Claim 1 wherein the aliphatic olefin hasa plurality of double bonds in a straight chain.

4. A method in accordance with Claim 1 wherein the aliphatic olefin isan alpha-olefin.

5. A method in accordance with Claim 1 wherein the ruthenium catalyst isruthenium metal.

6. A method in accordance with Claim 1 wherein the ruthenium catalyst isan organic ruthenium compound.

7. A method in accordance with Claim 1 wherein the ruthenium catalyst isan inorganic ruthenium compound.

8. A method in accordance with Claim 1 wherein the reaction mixtureadditionally contains an inert solvent.

9. A method in accordance with Claim 8 wherein the alkali metal salt ispresent in .a ratio of peracid oxidizing agent to alkali metal saltbetween about 4 to 1 and to 1.

10. The process in accordance with Claim 1 wherein the alkali metal saltis sodium acetate.

11. The process in accordance with Claim 1 wherein the alkali metal saltis sodium carbonate.

References Cited UNITED STATES PATENTS 3,409,649 11/ 1968 Keblys et a1.260-413

1. IN A PROCESS FOR THE CATALYTIC OXIDATION OF AN ALIPHATIC OLEFIN TOCARBOXYLIC ACIDS WITH A PERACID OXIDIZING AGENT IN THE PRESENCE OFRUTHENIUM CATALYST THE IMPROVEMENT WHICH COMPRISES ADDING TO THEREACTION MIXTURE AN ALKALI METAL SALT OF A LOWER FATTY, ACID, ORCARBONATE.